This application claims the priority of German Application No. 198 18 867.6, filed Apr. 28, 1998, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a selector for an automatic motor vehicle transmission and, more particularly, to a selector including a selector lever, a latching lever, a two armed rocker, latching surfaces and a control member.
The invention relates to all types of automatic transmissions, for example fully automatic and partially automatic gear boxes; in addition, so-called torque converter automatic transmissions and continuously variable transmissions with continuously variable transmission ratios with or without gears.
A selector of this type is described in German patent document DE-C 196 41 706 (corresponding to U.S. application Ser. No. 08/948,419, filed Oct. 10, 1997, the specification of which is incorporated by reference herein). The selector element is a pivotably mounted selector lever that can be pivoted in the direction of a park position P through a reverse position R into a neutral position N in which the torque transmission of the vehicle gearbox is interrupted. The lever can then be pivoted into at least one forward position D.
Latches are provided for positions P and N. The latches operate as a function of certain operating conditions. In the park position P, the selector lever is locked for as long as the vehicle brake is not actuated and the ignition key is not in the ignition lock (or the ignition is not switched on). As soon as the ignition key is inserted into the ignition lock (or the ignition is switched on) and the brake is actuated, the selector lever is released. This function is referred to in the following as the P latch. A latch is likewise provided for moving the selector lever from the neutral position N into the reverse position R, said latch being active for as long as the vehicle speed does not drop below a certain limit. This function is referred to in the following as the R latch. Moving the selector lever from D to N however is not impeded by this latch. These functions are achieved by the subject of the above-mentioned German patent document which has not yet been published.
A system is known from Japanese Patent document JP 3-239868 A in which the latching of the selector lever in the park position P and in the reverse position R can be released by energizing an electromagnet. The latching function is maintained by a spring force. Therefore, it is not possible to move the selector into the park position P in the event of an overall power failure in the entire vehicle system. As a result, it is also not possible to park the car safely because the ignition key can be removed from the ignition lock only when the selector lever is in the P position. In addition, a selector is known from Japanese Patent document JP 6-117526 A in which a selector lever is immovably connected with a latching link provided with latching cams. A selector for an automatic transmission with a selector lever is known from German Patent document DE-A-41 18 519, said lever being adjustable from a neutral position (N) into a forward driving position (D) and beyond these positions into one or more low-speed shift positions (1, 2). In the opposite direction, the lever is adjustable into a reverse position (R) and beyond the latter into a park position (P). A manual downshift from a higher speed to a lower speed is automatically blocked if a critical state of the vehicle would result from such a downshift.
The actuators that lock or unlock the latch are electromagnetic control elements and springs but can also be other elements. The latches are not supposed to be unlocked by the selector element as a result of the manual operating force of the driver if the operating conditions required for unlocking are not present. Such conditions can be, for example, a driving authorization by the driver, an ignition key in the ignition lock, and a vehicle speed below or above a certain limiting value. On the other hand, an actuator is supposed to be able to unlock the latch when all the operating conditions are met, but the driver exerts a manual actuating force on the selector element before these operating conditions are met. In this case, there is the danger that the mechanical latching elements will be so strongly pressed together by the manual actuating force at the selector lever that they can no longer be torn apart by an actuator, or the actuator would have to be of a size that was unacceptable as far as space requirements and weight were concerned or because of the operating heat developed by it. The larger an electromagnetic control element is, the greater the heat that it develops, especially if it is connected to current from the entire vehicle operating system. This situation arises in the selector in German Patent document DE-C 196 41 706 for example when a driver turns on the ignition and then exerts a manual actuating force on the selector lever before he actuates the vehicle brake. Since the electromagnetic actuator is supplied with electric current to unlock the latch when the vehicle brake is actuated, the force of the electromagnetic actuator must also overcome the forces of friction that result from the manual force on the selector lever. Thus, excessive frictional forces are absent only if the driver does not exert an actuating force on the selector lever until he has switched on the ignition and stepped on the brake. Additional selector devices are known from German Patent documents DE-A 34 19 168 and DE-A 41 20 379.
The invention is intended to achieve the goal of providing a compact, small design for a selector which can also lock and unlock reliably without requiring actuators which are larger and stronger than those in the prior art if a manual actuating force is exerted on the selector lever before the operating conditions required for unlocking the selector lever have been met.
This goal is achieved according to the invention by a selector for an automatic motor vehicle transmission, comprising a manual selector lever which is secured by a bearing arrangement and is mounted so that it can be moved back and forth into various positions to select transmission settings; a latching lever which is connected in terms of movement with the selector lever, and its end remote from the selector lever, which is on the side of the bearing arrangement facing away from the selector lever, having a contact surface pointing in one direction of movement and an additional stop surface that points in the opposite direction of movement; a two-armed rocker which is mounted to rotate around a rotational axis that extends transversely to the direction of movement of latching lever, two latching surfaces of which, alternately, one or the other latching surface is movable as a result of the rotation of the rocker in the direction of movement of stop surfaces or the latching lever, and which point in the direction of movement forward or backward away from one another; a spring which urges the rocker into a rocker end position in which a stop surface of the latching lever is blocked by a latching surface of the rocker; and a controllable motorized control member by which the rocker can be urged opposite to the spring force of the spring into the other rocker end position, in which the other stop surface of the latching lever is latched by the other latching surface of the rocker, characterized in that the stop surfaces are formed on outer sides of the latching lever, in that one latching surface is provided on one rocker arm and the other latching surface is located on the other rocker, each at a radial distance from the rotational axis of the rocker, and in that the movement path of the stop surfaces of the latching lever extends transversely over the rotational axis of the rocker.
Additional features of the invention are described herein.
According to the preferred embodiment of the invention, the P latch is passive so that it engages if the motor vehicle operating current fails, and the R latch is active so that it is deactivated when the motor vehicle operating current fails. This is accomplished by virtue of the fact that spring means are provided that urge the latching mechanism into a position that corresponds to the P latch and that control means are provided that are operated pneumatically, hydraulically or preferably electrically. The control means urge the latching mechanisms against the force of the spring means into a position that is associated with the R latch. As a result, the selector element can be set to the park position P even if the operating current fails while the selector element is in a position other than the park position P. This is important for parking the vehicle safely because in modern motor vehicles the vehicle key can be removed from the ignition lock only if the selector element is in the park position P.
The invention also has the advantage that the latch can be safely unlatched by the spring means or the controlled control member when a manual actuating force is applied by a driver to the selector element when not all of the operating conditions for unlatching are in place. For example, according to one preferred embodiment, the controlled control element (or in another embodiment, the spring member) can unlatch the device only if the ignition key is inserted and the ignition is possibly switched on and the vehicle brake is also actuated. In this case, the driver frequently exerts a manual actuating force on the selector element before he operates the vehicle brake. The invention has the advantage that the spring means or the controlled control member can "tear apart" the latching elements and thus bring them into an unlatched position when the operating conditions required for unlatching are met only after a manual actuating force is exerted on the selector element, for example only after the ignition is switched on and/or the brake is activated.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.